High-throughput detection and quantification of vitamin B ₁₂ in microbiome isolates using Escherichia coli

Vitamin B ₁₂ is an essential micronutrient produced only by prokaryotes, and animals must acquire it from their diet. Vitamin B ₁₂ is critical for the synthesis of methionine and propionyl-CoA metabolism. In humans, vitamin B ₁₂ deficiency has been linked to many disorders, including infertility and developmental abnormalities. The growing trend towards plant-based diets and the ageing populations increase the risk of vitamin B ₁₂ deficiency, and therefore, there is an increasing interest in understanding vitamin B ₁₂ biology. Accurate approaches for detecting and quantifying vitamin B ₁₂ are essential in studying its complex biology, from its biogenesis in Bacteria and Archaea to its effects in complex organisms. Here, we present an approach using the commonly available E. coli methionine auxotroph strain B834 (DE3) and a multi-well spectrophotometer to detect and quantify vitamin B ₁₂ from biological samples at picomolar concentrations. We further show that our quantification method for vitamin B ₁₂ is sufficient to reveal important differences in the production of vitamin B ₁₂ from vitamin B ₁₂ -synthesising bacteria commonly found in the microbiome of wild Caenorhabditis elegans isolates. Our results establish a high-throughput and simple assay platform for detecting and quantifying vitamin B ₁₂ using the E. coli B834 (DE3) strain.